mdsolar writes: "Insider threats are the most serious challenge confronting nuclear facilities in today's world, a Stanford political scientist says.

In every case of theft of nuclear materials where the circumstances of the theft are known, the perpetrators were either insiders or had help from insiders, according to Scott Sagan and his co-author, Matthew Bunn of Harvard University, in a research paper published this month by the American Academy of Arts and Sciences.

"Given that the other cases involve bulk material stolen covertly without anyone being aware the material was missing, there is every reason to believe that they were perpetrated by insiders as well," they wrote.

And theft is not the only danger facing facility operators; sabotage is a risk as well, said Sagan, who is a senior fellow at Stanford's Center for International Security and Cooperation and the Caroline S.G. Munro Professor in Political Science.

While there have been sabotage attempts in the United States and elsewhere against nuclear facilities conducted by insiders, the truth may be hard to decipher in an industry shrouded in security, he said.

"We usually lack good and unclassified information about the details of such nuclear incidents," Sagan said.

The most recent known example occurred in 2012 – an apparent insider sabotage of a diesel generator at the San Onofre nuclear facility in California. Arguably the most spectacular incident happened at South Africa's Koeberg nuclear power plant (then under construction) in South Africa in 1982 when someone detonated explosives directly on a nuclear reactor."